Berkeley's Argument for Immaterialism

Written by A.C. Grayling.

Berkeley's philosophical view is often described as an argument for "immaterialism", by which is meant a denial of the existence of matter (or more precisely, material substance.) But he also, famously, argued in support of three further theses. He argued for idealism, the thesis that mind constitutes the ultimate reality. He argued that the existence of things consists in their being perceived. And he argued that the mind which is the substance of the world is a single infinite mind – in short, God. These are four different theses, but they are intimately connected in Berkeley's presentation of them, the arguments for the first three sharing most of their premisses and steps. My chief purpose in what follows is to give an account of these arguments, their interactions, and the assumptions and methods underlying them. Doing so makes their strengths and weaknesses both conspicuous and perspicuous.

Berkeley's philosophical aim in arguing for these theses is to refute two kinds of scepticism. One is epistemological scepticism, which says that we cannot know the true nature of things because (familiarly) certain perceptual relativities and psychological contingencies oblige us to distinguish appearance from reality in such a way that knowledge of the latter is at least problematic and at worst impossible. The other is theological scepticism, which Berkeley calls "atheism" and which in his view includes not only views that deny the existence of a deity outright, but also Deism, for which the universe subsists without a deity's continual creative activity. In opposing the first scepticism Berkeley took himself to be defending common sense and eradicating "causes of error and difficulty in the sciences." In opposing the second he took himself to be defending religion.

The attack on theological scepticism is effected on a metaphysical rather than doctrinal level in P and D. Doctrinal questions receive more attention in such later writings as Alciphron. But in one important respect Berkeley saw his views as a fundamental contribution to natural theology, in that he thought they constitute a powerful new proof of the existence of a God.

Berkeley takes the root of scepticism to be the opening of a gap between experience and the world, forced by theories of ideas like Locke's which involve 'supposing a twofold existence of the objects of sense, the one intelligible, or in the mind, the other real and without the mind" (P86). Scepticism arises because "for so long as men thought that real things subsisted without the mind, and that their knowledge was only so far forth real as it was conformable to real things, it follows, they could not be certain they had any real knowledge at all. For how can it be known, that the things which are perceived, are conformable to those which are not perceived, or exist without the mind?" (ibid.) The nub of the problem is that if we are acquainted only with our own perceptions, and never with the things which are supposed to lie beyond them, how can we hope for knowledge of those things, or even be justified in asserting their existence?

Berkeley's predecessors talked of qualities inhering in matter and causing ideas in us which represent or even resemble those qualities. Matter or material substance is a technical concept in metaphysics, denoting a supposed corporeal basis underlying the qualities of things. Berkeley was especially troubled by the un-empiricist character of this view. If we are to be consistent in our empiricist principles, he asked, how can we tolerate the concept of something which by definition is empirically undetectable, lying hidden behind the perceptible qualities of things as their supposed basis or support? If the concept of matter cannot be defended, we must find a different account of experience and knowledge. Berkeley summarises his diagnosis of the source of scepticism, and signals the positive theory he has in response to it, in a pregnant remark in C: "the supposition that things are distinct from Ideas takes away all real Truth, & consequently brings in a Universal Scepticism, since all our knowledge is confin'd barely to our own Ideas" (C606).

A point that requires immediate emphasis is that Berkeley's denial of the existence of matter is not a denial of the existence of the external world and the physical objects it contains, such as tables and chairs, mountains and trees. Nor does Berkeley hold that the world exists only because it is thought of by any one or more finite minds. In one sense of the term "realist", indeed, Berkeley is a realist, in holding that the existence of the physical world is independent of finite minds, individually or collectively. What he argues instead is that its existence is not independent of Mind.

Berkeley's "New Principle"

Berkeley's answer to scepticism, therefore, is to deny that there is a gap between experience and the world–in his and Locke's terminology: between ideas and things–by asserting that things are ideas. The argument is stated with admirable concision in P1-6, its conclusion being the first sentence of P7: "From what has been said, it follows, that there is not any other substance than spirit, or that which perceives". All the rest of P, D, and parts of his later writings, consist in expansion, clarification and defence of this thesis. The argument is as follows.

Berkeley begins in Lockean fashion by offering an inventory: the "objects of human knowledge" are "either ideas actually imprinted on the senses, or such as are perceived by attending to the passions and operations of the mind, or lastly ideas formed by help of memory and imagination, either compounding, dividing, or barely representing those originally perceived in the aforesaid ways". Ideas of sense–colours, shapes, and the rest–are "observed to accompany each other" in certain ways; "collections" of them "come to be marked by one name, and so to be reputed one thing", for example an apple or tree (P1).

Besides these ideas there is "something which knows or perceives them"; this "perceiving, active being is what I call mind, spirit, soul or myself", and it is "entirely distinct" from the ideas it perceives (P2).

It is, says Berkeley, universally allowed that our thoughts, passions, and ideas of imagination do not "exist without the mind". But it is "no less evident that the various sensations or ideas imprinted on the sense, however blended or combined together (that is, whatever objects they compose) cannot exist otherwise than in a mind perceiving them" (P3).

From these claims it follows that the gap between things and ideas vanishes; for if things are collections of qualities, and qualities are sensible ideas, and sensible ideas exist only in mind, then what it is for a thing to exist is for it to be perceived - in Berkeley's phrase: to be is to be perceived: esse est percipi. "For what is said of the absolute [i.e. mind-independent] existence of unthinking things [i.e. ideas or collections of ideas] without any relation to their being perceived, that seems perfectly unintelligible. Their esse is percipi, nor is it possible that they should have any existence, out of the minds or thinking things which perceive them" (P3).

Berkeley knows that this claim is surprising, so he remarks that although people think that sensible objects like mountains and houses have an "absolute", that is, perception-independent, existence, reflection on the points just made show that this is a contradiction. "For what," he asks, "are the aforementioned objects but the things we perceive by sense, and what do we perceive besides our own ideas or sensations; and is it not plainly repugnant [illogical, contradictory] that any of these or any combination of them should exist unperceived? (P4)

The source of the belief that things can exist apart from perception of them is the doctrine of "abstract ideas", which Berkeley attacks in his Introduction to P. Abstraction consists in separating things which can only be separated in thought but not in reality, for example the colour and the extension of a surface; or which involves noting a feature common to many different things, and attending only to that feature and not its particular instantiations – in this way we arrive at the "abstract idea" of, say, Redness, apart from any particular red object (P Introduction 6-17). Abstraction is a falsifying move; what prompts the "common opinion" about houses and mountains is that we abstract existence from perception, and so come to believe that things can exist unperceived. But because things are ideas, and because ideas only exist if perceived by minds, the notion of "absolute existence without the mind" (i.e. without reference to mind) is a contradiction (P5).

So, says Berkeley, to say that things exist is to say that they are perceived, and therefore "so long as they are not perceived by me, or do not exist in my mind or that of any created spirit, they must either have no existence at all, or else subsist in the mind of some eternal spirit" (P6). And from this the conclusion it follows that "there is not any other substance than spirit, or that which perceives" (P7).

In sum argument is this: the things we encounter in episodes of perceptual experience – apples, stones, trees – are collections of "ideas." Ideas are the immediate objects of awareness. To exist they must be perceived; they cannot exist "without the mind." Therefore mind is the substance of the world.

Berkeley's defence of this argument from P7 onwards reveals the machinery that drives it, consisting of the interplay between three crucial commitments and the application of an analytic method which requires us to recognise three different levels of explanation – whose own interrelations, in turn, are pivotal to his case.

The Machinery of Berkeley's Argument

Let us take the question of the three levels first. Berkeley distinguishes between "strict", "speculative" or "philosophical" ways of understanding matters, and ordinary or "vulgar" ways of doing so. When we "think with the wise" we find it necessary to give explanations at what I shall label "level 1" and "level 3." When we "talk with the vulgar" we do so at "level 2" (see e.g. P34-40, esp. P37; 45-8, 3D234-5, C274).

Level 1 concerns the phenomenology of experience, consisting of the data of sensory awareness in the form of minima of colour, sound, and so for the other senses. Level 2 concerns the phenomena of experience – the tables, trees, and so forth, that we see and touch in the normal course of perception. The phenomenological level (call it level 1) is apparent to us only on a "strict and speculative" examination of experience.

Level 2 phenomena are constituted by level 1 data – not reductively, but mediated in a way revealed by a third, metaphysical, level of explanation (level 3), which describes the causal-intentional activity of mind (ultimately: of an infinite mind) in producing the level 1 data and the level 2 world constituted for us by the organisation, coherence, and character of the level 1 data (P25-9, 51-2, 2D216).

The analysis can be illustrated by Berkeley's account of causality, which is fundamental to his thesis (P25-9, 51-2, 2D216). At level 3 the world is described as consisting of spirits (minds) and their ideas. Spirits are active, ideas inert. What we take at level 2 to be a case of natural causality– the heat of a fire causing water in a kettle to boil – is, strictly, a succession of individual ideas (composed of level 1 data) caused in us by God (level 3) in such a way that the regularity and consistency of their relations establishes in us a custom of thinking in the familiar level 2 way. This application of the distinction of levels provides, moreover, the basis of the proto-Positivistic philosophy of science sketched by Berkeley later in P (P86-117).

It is a common mistake among commentators to describe Berkeley as a phenomenalist. The distinction of levels shows why they are wrong. Briefly, classical phenomenalism is the view that physical objects are ("logical") constructions out of actual and possible sense-data. The modal adverbs in that sentence serve to explain how the desk in my study exists when not currently being perceived, by showing that we take as true a counterfactual conditional stating that the desk could be perceived if any perceiver were suitably placed. That indeed defines what, on the phenomenalist view, it is for such objects to exist: namely, as at least enduring possibilities of perception. An essential commitment of phenomenalism, therefore, is that certain counterfactuals are to be taken as barely (that is, non-reductively) true; which says, in material mode, that the world contains irreducible possibilia.

Berkeley's view is completely different. The esse est percipi principle requires that a thing must be perceived – actually perceived – in order to exist. The perceivability of my desk when it is not currently being perceived (by a finite mind) is therefore cashed in terms of its actually being perceived (by an infinite mind). In phenomenalism there are only levels 1 and 2. It is a familiar problem for phenomenalism that level 2 cannot be reduced to level 1 without remainder, and that therefore level 1 can only be sufficient for level 2 if suitably supplemented. The supplement is acceptance of the bare truth of appropriate counterfactuals (and thus an ontology of possibilia). This exacts a high price for the explanatory shortfall. But for Berkeley there is no such shortfall; his third level of explanation shows how level 1 constitutes level 2, and simultaneously gives us a simple account of counterfactuals by having their truth-conditions fully statable in indicative terms: "If I were in my study I would see my desk" is true just in case "My desk is perceived by the infinite mind" is true ( = "the desk exists"). So on Berkeley's view possibility is relative to finite minds only – for the infinite mind whatever is, is actual. (Whether any of it is also necessary is of course a different and further matter).

So, says Berkeley, to say that things exist is to say that they are perceived, and therefore "so long as they are not perceived by me, or do not exist in my mind or that of any created spirit, they must either have no existence at all, or else subsist in the mind of some eternal spirit" (P6). And from this the conclusion it follows that "there is not any other substance than spirit, or that which perceives" (P7).

In sum argument is this: the things we encounter in episodes of perceptual experience – apples, stones, trees – are collections of "ideas." Ideas are the immediate objects of awareness. To exist they must be perceived; they cannot exist "without the mind." Therefore mind is the substance of the world.

Berkeley's defence of this argument from P7 onwards reveals the machinery that drives it, consisting of the interplay between three crucial commitments and the application of an analytic method which requires us to recognise three different levels of explanation – whose own interrelations, in turn, are pivotal to his case.

The Machinery of Berkeley's Argument

Let us take the question of the three levels first. Berkeley distinguishes between "strict", "speculative" or "philosophical" ways of understanding matters, and ordinary or "vulgar" ways of doing so. When we "think with the wise" we find it necessary to give explanations at what I shall label "level 1" and "level 3." When we "talk with the vulgar" we do so at "level 2" (see e.g. P34-40, esp. P37; 45-8, 3D234-5, C274).

Level 1 concerns the phenomenology of experience, consisting of the data of sensory awareness in the form of minima of colour, sound, and so for the other senses. Level 2 concerns the phenomena of experience - the tables, trees, and so forth, that we see and touch in the normal course of perception. The phenomenological level (call it level 1) is apparent to us only on a "strict and speculative" examination of experience. Level 2 phenomena are constituted by level 1 data – not reductively, but mediated in a way revealed by a third, metaphysical, level of explanation (level 3), which describes the causal-intentional activity of mind (ultimately: of an infinite mind) in producing the level 1 data and the level 2 world constituted for us by the organisation, coherence, and character of the level 1 data (P25-9, 51-2, 2D216).

The analysis can be illustrated by Berkeley's account of causality, which is fundamental to his thesis (P25-9, 51-2, 2D216). At level 3 the world is described as consisting of spirits (minds) and their ideas. Spirits are active, ideas inert. What we take at level 2 to be a case of natural causality– the heat of a fire causing water in a kettle to boil – is, strictly, a succession of individual ideas (composed of level 1 data) caused in us by God (level 3) in such a way that the regularity and consistency of their relations establishes in us a custom of thinking in the familiar level 2 way. This application of the distinction of levels provides, moreover, the basis of the proto-Positivistic philosophy of science sketched by Berkeley later in P (P86-117).

It is a common mistake among commentators to describe Berkeley as a phenomenalist. The distinction of levels shows why they are wrong. Briefly, classical phenomenalism is the view that physical objects are ("logical") constructions out of actual and possible sense-data. The modal adverbs in that sentence serve to explain how the desk in my study exists when not currently being perceived, by showing that we take as true a counterfactual conditional stating that the desk could be perceived if any perceiver were suitably placed. That indeed defines what, on the phenomenalist view, it is for such objects to exist: namely, as at least enduring possibilities of perception. An essential commitment of phenomenalism, therefore, is that certain counterfactuals are to be taken as barely (that is, non-reductively) true; which says, in material mode, that the world contains irreducible possibilia.

Berkeley's view is completely different. The esse est percipi principle requires that a thing must be perceived – actually perceived – in order to exist. The perceivability of my desk when it is not currently being perceived (by a finite mind) is therefore cashed in terms of its actually being perceived (by an infinite mind). In phenomenalism there are only levels 1 and 2. It is a familiar problem for phenomenalism that level 2 cannot be reduced to level 1 without remainder, and that therefore level 1 can only be sufficient for level 2 if suitably supplemented. The supplement is acceptance of the bare truth of appropriate counterfactuals (and thus an ontology of possibilia). This exacts a high price for the explanatory shortfall. But for Berkeley there is no such shortfall; his third level of explanation shows how level 1 constitutes level 2, and simultaneously gives us a simple account of counterfactuals by having their truth-conditions fully statable in indicative terms: "If I were in my study I would see my desk" is true just in case "My desk is perceived by the infinite mind" is true ( = "the desk exists"). So on Berkeley's view possibility is relative to finite minds only – for the infinite mind whatever is, is actual. (Whether any of it is also necessary is of course a different and further matter).

Many of the difficulties standardly alleged in Berkeley's argument vanish when understood in light of the three-level analysis. Illustrations of this occur in due place below.

As noted, three crucial commitments interact with the distinction-of-levels thesis to underwrite Berkeley's argument. They are commitments to empiricism, to the epistemic character of modality, and, as we have already seen, to the vacuity of the notion of abstract ideas. It might be more accurate to describe the two first as commitments and the third as the conclusion of an argument; but because the two first are premisses of that argument, and because all three powerfully combine in the process of refuting scepticism and establishing spirit as the only possible substance, it is convenient to take them together.

Berkeley is a rigorous empiricist; we are not entitled to assert, believe, or regard as meaningful, anything not justified by experience. The constraint is austerely applied: level 2 is exhaustively explained by level 1 under government of the level 3 causal-intentional story (see e.g. P38). It might appear that Berkeley is less rigorous in his empiricism than Hume because he introduces the notion of "notions" to explain our knowledge of spirit (other minds and God), which seems expressly to involve a non-sensuous epistemic source, and therefore to conflict with his notebook commitment to the strong principle nihil est in intellectu quod non prius fuit in sensu (C779).But we should allow Berkeley at least as much latitude as Locke claims in countenancing intellectual sources of experience. In this sense notions are the counterpart of "ideas" in Berkeley's sense (mental contents) in the experience of encountering minds through a certain class of their effects.

Of course, the ideas that constitute the world are the effects of God's causal influence on our sensory modalities, and are therefore encountered as level 2 physical objects in the standard way. But Berkeley argues that from the character of these ideas and their relations we grasp something further, viz. that a particular sort of mind wills them (this is part of his argument for taking it that the world's substance is a deity somewhat of the personal type offered in revealed religion. ) Parallel reasoning applies to finite spirits. In DeM Berkeley discusses the kind of experience that has self-awareness as its object; he calls it "reflexion" (DeM 40). But at P27 and elsewhere we learn that we have knowledge of spirit by its effects, and infer therefore that notions too are the objects of awareness: a second-order awareness, so to speak, consisting in grasp of the significance of ideas acquired in the standard sensory way. The signal point is that without experience as such we do not come by notions; so Berkeley's empiricism is unequivocal (P22, 1D200).

The second and third commitments - that possibility is an epistemic concept, viz. conceivability; and that there are no abstract ideas - arise from the first (P Intro. 9 et. seq., P4, 1D177, 3D194). His chief form of argument is indeed a conceivability argument: we cannot conceive colour apart from extension, ideas apart from mind, existence apart from perception (P4, 7, P Intro. 8, 9). In both cases the dependence on the empirical commitment is direct. Concepts lack content unless they are empirically derived; the thesis is forcefully stated in V where Berkeley asks whether it is possible for anyone "to frame in his mind a distinct abstract idea of visible extension or figure exclusive of all colour: and on the other hand, whether he can conceive colour without visible extension?" and replies, "For my own part, I must confess I am not able to attain so great a nicety of abstraction: in a strict sense, I see nothing but light and colours, with their several shades and variations" (V130). To "frame in the mind" is to conceive; the "strict sense" is the level 1 or phenomenological sense; concepts of extension and figure therefore derive their content wholly from their experiential source, namely, visual minima of "light and colour".

There is an important point to be noted at this juncture, anticipated in the presentation given above of Berkeley's P1-7 argument. It is that where Berkeley uses his habitual locution "without the mind" we do better to use "without reference to mind." The point of this recommendation is illustrated by what is at stake in contemporary debates about "realism" and "anti-realism". In this connection realism is the claim that the entities in a given domain exist independently of knowledge or experience of them. The anti-realist denies this. One way of sketching why he denies it is offered by the idiom of relations. Thus recast, realism is the view that the relation between thought or experience and their objects is contingent or external, in the sense that description of neither relatum essentially involves reference to the other. On the anti-realist's view, to take the thought-object relation as external is a mistake at least for the direction object-to-thought, because any account of the content of thoughts about things, and in particular the individuation of thoughts about things, essentially involves reference to the things thought about – this is the force of the least that can be said in favour of notions of broad content. So realism appears to offer a peculiarly hybrid relation: external in the direction thought-to-things, internal in the direction things-to-thought. It is a short step for the anti-realist to argue that thought about (perception of, theories of) things is always and inescapably present in, and therefore conditions, any full account of the things thought about; the poorly-worded "Master Argument" in Berkeley, aimed at showing that one cannot conceive of an unconceived thing, is aimed at making just that elementary point (P23, 1D200). The best example of such a view is afforded by the Copenhagen interpretation of quantum theory, in which descriptions of quantum phenomena are taken essentially to involve reference to observers and conditions of observation. Such a view does not constitute a claim that the phenomena are caused by observations of them; no more does anti-realism claim this in respect of the subject-matters in which it argues its case, for it is not a metaphysical but an epistemological thesis. This is why anti-realism is not idealism, for idealism is a metaphysical thesis about the constitution of reality (namely: that reality is mental), not, as anti-realism is, an epistemological thesis about the relation of thought or experience to that reality. In expressing his view the anti-realist therefore does best to say: "anti-realism is the thesis that, with respect to a given domain, any full description of the objects of thought or experience in that domain has to make essential reference to the thinker or experiencer and the conditions under which the thinking or experience occurs".

And this is the least that Berkeley means by "within the mind". Of course, it is clear that Berkeley is not only an anti-realist but also an idealist, and that the latter, metaphysical, thesis, depends crucially on his argument for the former, epistemological, thesis. The fact that anti-realism and idealism are independent theses (one can be committed to either without being committed to the other) is masked in Berkeley's case by the fact that his "in the mind" idiom does duty both for "with essential reference to mind" and "made of mind-stuff". But it is not hard to know which reading is intended at any point in his exposition.

The Argument Restated

Equipped with this account of Berkeley's commitments and method, we can restate his argument as follows. If we examine the phenomenology of consciousness (level 1) we see that it consists of sensory data, notions, and compounds of either or both of these. Experience is generally orderly, giving rise to the familiar phenomena of level 2 – apples and trees, stones and books (P1). We are also intimately acquainted with ourselves as the subjects of this experience, and not merely as passive recipients of it but causally active participants who will, imagine, and remember (P2). Nothing of level 1 can be conceived without reference to the minds for which they exist as the contents of consciousness. But because the phenomena of level 2 are constituted by data of level 1, neither therefore can the phenomena of level 2 be conceived independently of the minds for which they are phenomena (P3). It is commonly held that sensible objects exist independently of mind; but this, on the foregoing, is a contradiction, which rests on the mistaken doctrine of abstraction (P4, 5). It follows that the only substance there can be is mind or spirit (P6, 7).

The argument has made no explicit mention of material substance; the first full-dress appearance of matter, as the focus of "received opinion" in this debate, has to wait a further ten paragraphs (P16-17). But the denial of its possibility has already been registered, for if things are ideas, and ideas are essentially mental, then nothing other than mind can substantiate them. The doctrine that there is "unthinking stuff" which is the substance of things qua collections of ideas is accordingly an obvious "repugnancy" (contradiction): for how can an unthinking thing have ideas? (P7)

A crucial consideration for Berkeley in rejecting the concept of material substance is that there are no empirical grounds for it; its philosophical supporters (he has Locke in mind) "acknowledge they have no other meaning annexed to those sounds, but the idea of being in general, together with the relative notion of its supporting accidents" (P17). Berkeley finds the concept of "being in general" the most "abstract and incomprehensible" he has ever encountered, and he has no time for the metaphor of "support" invoked to explain the relation between matter and its accidents. But more importantly still, the only thing which we are entitled to say is causally efficacious is spirit or mind (P26-7); ideas are the effects of the causal activity of mind, whether our own or that of an infinite spirit (P28-33).

In the course of unfolding his argument Berkeley tells us that although there is a distinction between primary and secondary qualities, they are the same in one crucial respect: they are both sensible properties, and therefore cannot exist otherwise than as ideas, and therefore again cannot exist otherwise than in relation to mind (P9-15). He also points out that since nothing but an idea can be like an idea, the seductive thought that ideas are resemblances or copies which represent non-ideas makes no sense: can we, he asks, "assert that a colour is like something which is invisible; hard or soft, like something which is intangible; and so of the rest"? (P8)